than 3:2, like 16:9 or 16:10? Given the popularity of widescreen TVs and computer monitors with wide aspect ratios, and that most photos are viewed on a screen, rather than printed, and that the eye perceives a field of view wider than it's taller, one of these two aspect ratios seem to make more sense.

I'm not saying that 16:9 or 16:10 are OPTIMAL aspect ratios for the human eye; just that they are better than 3:2. I wouldn't mind 2.39:1, either. Anything wider than 3:2, really.

Am I missing something?

I'm not saying that there should be sensors with only one aspect ratio (16:9), just that it makes sense for it to be the most popular one, just as most laptop screen sizes are 13-15 inches. There are 11 inch laptops, and 17 inch ones, but the most popular sizes are 13-15 inches. By the same token, I understand that there has been and will be sensors of different aspect ratios. My question is just about why the most popular one is not 16:9 or :10.

I've always wondered the opposite: Why aren't all sensors 1:1? That must be the optimal usage of the lens, right? (Hmm ... no, of course a circular sensor would be "optimal", but that seems too far from how we humans enjoy pictures ... )
– Erik TjernlundJan 6 '14 at 9:38

Interesting point. I assume by optimal you mean that it uses the largest fraction of the image circle.
– Vaddadi KartickJan 6 '14 at 10:20

By "optimal", I mean, collecting the most amount of light from the lens. I've always thought a Hasselblad-like 1:1 square would be much better, but I really liked @drfrogsplat's answer, pointing out the sensor should be as much of a circle as possible and then the crop can be made in software.
– Erik TjernlundJan 9 '14 at 8:54

1. Most photos are viewed on a screen, but not fullscreen. They're embedded in articles. 2. We have a wide field of vision, but the area we perceive as sharp and we can focus on is not wide. 3. Most photos don't aim to accurately reproduce human perception; instead they show one subject we focus on. Wide is not usually optimal for this. Nor is it usually the most pleasing one. Paintings are almost never as wide as 16:9 as this is not a good aspect ratio for showing most subjects. 4. Cinema is different: it does aim to fill out your field of view without putting subjects in the edges.
– SzabolcsJan 5 '15 at 17:31

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Also, I find 16:9 a really silly ratio for small laptop screens. It's really meant for watching movies, not for computer work. It works for large high resolution screens where we're likely to arrange windows side by side, but the smaller a screen gets the more awkward it is. Thankfully Apple stayed with the more convenient 16:10 and an iPad has 4:3.
– SzabolcsJan 5 '15 at 17:39

7 Answers
7

A few Panasonic cameras actually do have wider sensors to match 16:9. However, this hasn't really catapulted these models to success, or caused a lot of other camera makers to follow. If this were important in the market, you'd think that it would, just like the launch of the Sigma DP1 paved the way for a new class of large sensor, fixed lens compact cameras.

So, why not?

Chiefly, I think they are:

People still do print, and think of photographs in terms of traditional prints.

People who share photos online are often sharing them in the context of being embedded in some social media site or blog, with surrounding elements and not necessarily full screen. On my desktop or laptop screen, I'm looking at these in a browser window which isn't stretched to monitor width (because a wide web browser makes it slow to read text which isn't in columns), and on my phone I'm generally looking in portrait mode.

16:9 may match most monitors and TVs right now, but it's kind of an awkward compromise format. Specifically, it's a compromise between the traditional "acadamy ratio of 4:3 and modern anamorphic widescreen for movies. For photography, even as digital device usage shifts the way we view photos, it's not really particularly great. In fact, the trend (possibly started by Instagram, but there's more to it than that) is for mobile to encourage square format, not widescreen.

Continuing that thought but from a different direction: photography has a different history than cinema, and its most direct ancestor is painting. An analysis of paintings of the canonical masters of that art shows a tendency towards almost-square formats around 5:4. Why would we discard that legacy just because the needs of TV take consumer electronics wide-screen?

If the sensor is 16:9, that's better for wide angle landscape view, but horribly narrow for portrait view.

A wide format sensor would record more from the edges of the image circle, where image quality is generally lower. This would force larger and more expensive lenses if you want the extra width to be actually useful.

Last but certainly not least: most cameras provide a mode to crop to 16:9 in-camera. This is sightly "wasteful", both in terms of lost pixels at the top and bottom and because wide-format sensors could be slightly wider, but it's only by a few percent, and given the other things, not worth it.

There may be other reasons, but overall I think people just don't see it as important.

On your point #6, you might mention the xpan from Hasselblad. Beautiful camera but much more expensive lenses to be able to handle the 24x65mm frame. The image circle needed to be 70mm across - nearly twice as large as the 24x32mm frame. And to try to combat light fall off from such a large image circle you got a custom Center ND grad. Btw, if you ever have the spare money I would be grateful for the 30mm f/5.6 lens. Three stops slower than the 35mm f/2, it shouldn't cost that much more for the larger image circle.
– user13451Jan 10 '16 at 3:31

I can't speak for the industry, but I can certainly say why I wouldn't want to buy a camera with a 16:9 (or worse, wider) sensor:

It doesn't suit my creative goals or assist with my task of simplifying the world.

The 2:3 ratio is already far too narrow for vertical compositions, which I typically crop down to 4:5 or 5:7. Having a 9:16 sensor would further narrow the field of view and reduce resolution further.

A wider aspect ratio is a poorer match for the light circle from the lens, capturing less light on its smaller surface area. Sensor technology continues to improve, but a larger lit area will always have an advantage over a smaller one.

With a high-resolution sensor (for prints) or a low-resolution display (electronic) cropping to change the aspect ratio has no downside as long as the final crop was anticipated in the original composition.

My desired artistic end product is the printed photo. The Widescreen aspect ratio does not suit my goal.

Even though I can crop to any aspect ratio I choose for electronic display, I almost never use 16:9. The widest I routinely use is 1:1.618.

I'm not arguing that 3:2 is the best possible aspect ratio, and only six of my thirteen cameras shoot in it natively. But one of those remaining seven cameras has a sensor with a variable aspect ratio, and I predominantly choose 3:2, occasionally 4:3, and only rarely use its 16:9 option.

I think the better question is why image sensors aren't (close to) ciruclar, rather than wider.

The image circle focussed onto the sensor is, well, a circle. In some sense, in the ideal case, you would capture the entire circle, and then choose what portion of that circle to use as your image. I say 'ideal' from the point of view of maximising framing capabilities, not making it easy to use.

The popularity of rectangular photos (and videos) has meant selecting a 3:4 or 2:3 section of that circle, to avoid having to crop every single photo—instead we frame it in the camera, and most of the time it's much simpler. But if you want anything other than the native aspect ratio, you're going to be cropping.

The only real advantage of 16:9 would be if you always use 16:9, then you're getting a slightly cheaper sensor (because you could shave a little off the top and bottom) and about 8% more area than the 16:9 crop from a 3:2 frame. On the other hand, any 'squarer' crops from that 16:9 frame will be 28% less area than they'd have otherwise been from a 3:2 sensor (to fit the same image circle).

A square sensor, on the other hand, gives you 63% more area for a square image, compared to a square crop from a 3:2 sensor, while 4:3, 3:2 and 16:9 are 10 to 39% smaller compared to the same aspect-ratio crops from a 3:2 sensor.

Cost aside, I think the ideal camera would have a (roughly) circular sensor, with similarly circular RAW files, but cropped JPEGs. You'd set your desired aspect ratio, and the camera would apply the appropriate crop. Shooting RAW, you could quickly switch between portrait and landscape without even rotating the camera. And you'd always get the maximum resolution possible for any aspect ratio (1:1 through 16:9), for the given sensor pixel pitch.

Here's a table with some comparisons of crops from different sensor sizes. The columns specify how the native sensor is limited (i.e. by image circle, or a specific sensor aspect ratio at its maximum size in the image circle), the rows specify the shape of the final (cropped) image, and each cell shows the percentage of the image circle covered by said crop from said sensor.

Naturally the best result comes from using the sensor at its native aspect ratio (and the square maximises the rectangular coverage of a circle).

A 16:9 image from the 16:9 vs 3:2 sensors won't be vastly different (about 50–54% of the image circle), but the differences in the other crops between these sensors are quite significant. The best 'all round' sensor seems to be 4:3 or 3:2 (though really depends mostly on whether you're more likely to go squarer or wider than the native).

The first column shows the ideal for any crop aspect ratio, which would only be achievable with a circular sensor (or a larger sensor that covers the full image circle).

Thanks, drfrogsplat. I don't think it's realistic to ignore cost. Circular sensors mean that a lot of space is wasted between sensors on a wafer, so we'll have to stick with rectangular ones.
– Vaddadi KartickJan 6 '14 at 6:10

I don't see any reason to crop captured JPEGs; since the JPEG format allows parts of the image to be compressed more than other parts, the area beyond the sensor wouldn't have to waste much space.
– supercatJun 10 '14 at 17:20

If the camera doesn't crop the photo, the user must, which is a hassle. It's not about the file size. Maybe if you're capturing a RAW, you can keep the entire photo, and crop what you want, while in JPEG mode it can auto-crop.
– Vaddadi KartickNov 4 '14 at 6:20

The common aspect ratio of 4:3 of digital camera is narrower and was decided because it was the ratio of computer-screens at the time, so I understand why you would be inclined to think that a 16:9 or 16:10 would be more appropriate now.

The 3:2 aspect-ratio adopted from film is slightly wider and relatively easy to compose with. When formats get wider, they make it harder to compose. Of course, the suit better some subjects but the point is that what guides the format is much more often the subject than the medium. In some cases you have a medium such as a frame you want to fill edge-to-edge but just because that is the size you want does not mean your subjects will nicely fit in a specific-size frame.

There are cameras with wider-sensors, including 16:9 ones. More common though are sensors with an in-between aspect-ratio whose corners exceed the imaging-circle of the lens. Those cameras let users select different aspect-ratios while mostly preserving resolution and more importantly IMHO viewing angle. You can notice this on Panasonic and Fuji cameras when you change the aspect-ratio, both vertical AND horizontal resolution change.

Photos aren't always displayed exclusively as photos on screen in their entirety or in one orientation.

You can see this difference in usage in action when you compare photographic with video equipment. Video kit is used exclusively oriented in "landscape" and the sensor sizes match the screen/output parameters.

Just looking around on websites and in print will show you that stills are used in a wide range of aspect ratios and framing to suit the subject and whatever you choose as a manufacturer will be inappropriate to someone. I don't think you'd get much love from the medium format users for giving them a 16:9 sensor for example.

As for are you missing something? Well, if you only apply the use case as you have then yes, you probably are missing something. Such as, without other use cases there's no argument for sensors to go beyond 2mp or for colour depth to go beyond 8 bits since most displays can't show it.

James, I didn't say that photos are displayed EXCLUSIVELY on screen, just that they most often are. And I know that photos are used in a wide range of aspect ratios, but that's also an argument against 3:2 sensors. Finally, I didn't mean to suggest that specific niches, like medium-format, should use 16:9, just that most cameras should. I actually had consumer cameras in mind: ones costing below $1000. Most monitors today use 16:10 or 16:9, but you can buy a monitor of a different aspect ratio. I was wondering why that's not the case for camera sensors as well. Thanks for your help.
– Vaddadi KartickJan 5 '14 at 14:02

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My answer is to demonstrate that the question is based on an invalid assumption of how people use cameras for photography. 'Primarily' can substitute for 'exclusively' but a one-word edit seems a bit pointless.
– James SnellJan 5 '14 at 14:25

I'm afraid we still seem to be talking past each other. Can you tell me what assumption in my question is invalid? I was trying to say that your point that people take photos of different aspect ratios isn't an argument against 16:9 any more than it's an argument against 3:2.
– Vaddadi KartickJan 5 '14 at 14:32

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The implication that people primarily use 16:9 displays and look at images on their screen in landscape format to match that display is an invalid assumption. After that any proposal or rejection of any capture parameter purely because of an uncommon output scenario will be invalid.
– James SnellJan 5 '14 at 15:23

Okay, so what according to you is the most common viewing medium? Do you think most of the photos taken in the world (not just by you, or enthusiasts on photo.SE, but all camera users, including smartphones) are printed?
– Vaddadi KartickJan 5 '14 at 15:46

The 3:2 aspect ratio was popular long before digital cameras. In fact, the 3:2 aspect ratio was adopted for digital cameras because it was so already popular for 35mm film cameras. In the film world, while the 3:2 aspect ratio is popular it's certainly not the only option: you can find plenty of square-format cameras and other formats in between square and 3:2 -- 4x5 (inches) and 6x4.5 (centimeters) are common.

On the wide side, a few companies made 6x17 (for a ratio of 3:1) cameras. For a smaller package, there are cameras that use 35mm film to shoot a double-wide (24x72mm), also for a 3:1 aspect ratio.

Sorry, Dan, but that doesn't answer my question, at least not that I can tell. Why aren't 16:9 sensors common, given today's reality (widescreen TVs and monitors, where most photos are displayed)?
– Vaddadi KartickJan 5 '14 at 14:04

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Historically, 16:9 has not existed, let alone mattered. Besides, there are many other formats people have always been able to choose between.
– Dan WolfgangJan 5 '14 at 14:13

Sure, the history is fine, but what worked in the past doesn't necessarily work best now, given that photos are nowadays viewed on 16:9 screens. Sure, there are many formats, but I was curious why 16:9 is not the most popular format for sensors.
– Vaddadi KartickJan 5 '14 at 14:33

It may be worth remembering the APS film format, which recorded natively in 16:9 aspect, but could also be printed as 3:2 or 3:1. As an historical footnote it doesn't really have any relevance on the recent proliferation of wide-screen electronic displays, but there was – briefly – a format that boasted having a 'High Definition' aspect ratio.
– mprJan 5 '14 at 15:58

I think it all boils down to manufacturing costs. From that standpoint, I imagine that the most cost efficient aspect ratios would be 2:1 for televisions and 1:1 for cameras. I'd actually be happy with that.